A standard metered-dose inhaler, such as sold under the trade name "Flovent" by GlaxoWellcome, "Proventil" or "Vanceril" by Key Pharmaceutical, or "Aerobid" by Forest Pharmaceuticals, comprises a small pressurized medication-filled cartridge and a holder formed with a short tubular mouthpiece. After shaking the device the mouthpiece is inserted into the mouth between the lips and teeth. Then as the patient takes a slow deep breath the cartridge is depressed to release a puff of the medication that is then drawn down into the lungs, normally to apply an anti-inflammatory agent to them.
Such a system is extremely effective only if used perfectly. That is the puff of medication must be blown into the oral cavity while the patient is inhaling so that it will travel to the lungs. The problem is that it is invariably being used by those suffering from breathing difficulties who are in fact often gasping for breath when the device is being used so that getting the procedure correct is a problem, in particular for children.
This has lead to the development of aids that are used with an inhaler. One such as described in U.S. Pat. No. 5,012,804 has a rigid cylindrical chamber provided at one end with a tubular extension serving as mouthpiece and of substantially the same size and shape as the mouthpiece of the inhaler. The other end of the chamber is provided with a hole into which the mouthpiece of the inhaler is fitted and a one-way valve at this other end allows air to be drawn into the chamber. Thus, after fitting the inhaler to the chamber, the user places the mouthpiece of the holding chamber in his mouth, actuates the inhaler to shoot a puff of the medication into the chamber, and then slowly inhales to draw in the charge from the chamber. Such an arrangement can even allow the user to draw in the medication in two breaths.
Another such system sold under the trade name "InspirEase" by Schering Pharmaceutical has a collapsible chamber and the inhaler cartridge is fitted to the mouthpiece between the chamber and the outer end that is inserted into the patient's mouth. With this system the chamber is expanded and the medication is blown into it, then the user breathes in the air from the chamber until same is completely collapsed. Once again this system allows the dose to be consumed in two breaths.
The disadvantage of these known systems is that they still require the patient to use them very, very carefully. The medication must be drawn straight into the oral cavity so that it then passes down into the lungs. If, for instance, the mouthpiece is only gripped between the lips, it is possible for the incoming stream of air to impinge on the front teeth so that much of the medication will simply be applied as a film to the teeth where it is does no good. These administration problems are particularly great with children who often cannot master the procedure for properly taking in the needed drug.